AK Water Operator flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

MCL

Maximum Contaminant Level: the highest legally allowed concentration of a contaminant in drinking water, enforceable under the Safe Drinking Water Act.

Secondary standard (SMCL)

A non-enforceable aesthetic guideline for contaminants affecting taste, odor, color, or appearance, such as iron, manganese, or sulfate.

Turbidity limit

For conventional filtration, turbidity must be 0.3 NTU or less in at least 95% of monthly samples and never exceed 1 NTU.

3-log Giardia removal

Surface Water Treatment Rule requires 99.9% removal or inactivation of Giardia lamblia for systems using filtration.

Nitrate MCL

The enforceable limit for nitrate is 10 mg/L as nitrogen, protecting infants from methemoglobinemia (blue baby syndrome).

Velocity gradient (G)

A measure of mixing intensity in coagulation and flocculation, typically 10-75 per second for flocculation and 100-300 for rapid mix.

Surface overflow rate

Sedimentation design parameter equal to flow divided by basin surface area, typically 0.5-1.0 gpm/ft2 for conventional plants.

CT value

Product of disinfectant residual concentration in mg/L and contact time in minutes, used to determine pathogen inactivation credit.

Backwash media expansion

Filter backwash should expand the media bed 15-25% to release captured particles without washing media out of the filter.

Minimum distribution pressure

Distribution systems must maintain at least 20 psi under normal and emergency conditions to prevent backflow and contamination.

Air gap

The highest level of cross-connection protection: a physical separation between the water supply outlet and the flood-level rim of a receiving vessel.

Unidirectional flushing

A flushing method that isolates pipe sections and pushes water at 2.5-5 ft/s from clean to dirty areas to scour sediment.

Main disinfection after repair

New or repaired mains are chlorinated to 25-50 mg/L for 24 hours or per AWWA C651, then flushed and tested for coliforms.

Pump head from pressure

Head in feet equals pressure in psi multiplied by 2.31; conversely, psi equals feet of head divided by 2.31.

Brake horsepower formula

Brake horsepower equals (gpm x head in feet) divided by (3960 x pump efficiency), giving power delivered to the pump.

Affinity laws

For a centrifugal pump, flow varies with speed, head with speed squared, and power with speed cubed.

Cavitation

Vapor bubbles form and collapse when NPSH available is less than NPSH required, causing noise, vibration, and impeller damage.

NPSH

Net Positive Suction Head: the absolute pressure energy at the pump suction, available versus required, to prevent cavitation.

HOCl versus OCl-

Free chlorine exists as hypochlorous acid and hypochlorite ion; HOCl is the stronger disinfectant and dominates below pH 7.5.

Chlorine demand

The difference between chlorine dose applied and the free chlorine residual remaining after a specified contact time.

TTHM MCL

The maximum contaminant level for total trihalomethanes is 0.080 mg/L, evaluated as a locational running annual average.

HAA5 MCL

The maximum contaminant level for five haloacetic acids is 0.060 mg/L, evaluated as a locational running annual average.

Chloramination ratio

Monochloramine forms best at pH 8-9 with a chlorine-to-ammonia weight ratio near 5:1, reducing regulated disinfection byproducts.

DPD method

A colorimetric test for free and total chlorine; total minus free approximates combined chlorine (chloramines).

Jar test

A bench-scale test simulating rapid mix, flocculation, and settling at varying coagulant doses to determine optimal treatment conditions.

Bacteriological holding time

Coliform samples must be chilled and analyzed within holding time, typically 8 hours when chlorine residual is measured, 30 hours otherwise.

Tier 1 public notice

Public notice required within 24 hours for violations posing immediate health risk, such as E. coli detection or failure to maintain pressure.

Consumer Confidence Report

An annual report delivered to customers by July 1 describing source water, detected contaminants, and compliance for the prior year.

Lead action level

The 90th percentile lead concentration of 0.015 mg/L; exceedance triggers corrosion control treatment and public education.

Confined space oxygen range

Acceptable oxygen for entry is 19.5-23.5 percent; outside this range requires ventilation and respiratory protection before entry.

Lockout/tagout

A procedure isolating hazardous energy sources before maintenance, verifying zero energy state to prevent unexpected startup or release.

Dose formula

Pounds of chemical equals dose in mg/L multiplied by 8.34 and by million gallons treated.